The present invention generally relates to a method and apparatus for detecting the presence of rock during coal or ore mining operations.
A more effective way to control solid mineral mining equipment, or miners, has been greatly desired by the mining industry. Many concepts have already been tried, over a period of many years, to improve mining controls to increase the amount of coal, or other mineral, cut by the mining equipment and to decrease the amount of undesirable rock cut by the mining equipment. Many of these concepts involve “guidance” systems that direct or point the miner where to cut, based on predictions or assumptions related to the location of the mineral-rock interface. These predictions or assumptions are typically based on data or information obtained from the experience of the mining equipment from previous cuts.
One seemingly simplified approach employs repetitive cycles. A computer is instructed by the miner operator to perform specific cycles or the control system is programmed to memorize operator actions over a cycle and duplicate them. This approach does not work well because of the high variability of the rock and mineral formations and operational considerations. This approach is particularly ineffective when applied to continuous miners, because the miner rides on the floor that has been cut resulting in cutting errors (e.g., leaving an excessive layer of coal on the floor, or cutting excessively down into the rock on the floor) for one cut tending to be amplified for subsequent cuts.
In the case of long-wall mining there is some opportunity to utilize what has been learned on one pass along the mineral face to improve upon cutting strategy for the next pass along the face. One approach utilizes a memory system to log the profiles of the rock face at the floor and roof on one pass and then to use this knowledge to influence the cutting as the cutters pass along the same face, going in the opposite direction. This approach has been of only limited success because the rock face profile on one pass does not exactly reflect the needed rock face profile of the next pass and because there is much variability in the formations and mining operations. Consequently, such equipment and operation are limited in their efficiency in cutting to the rock-coal interface using guidance strategy.
Gamma detectors have, over the years, shown promise in detecting the location of the rock-wall interface for both continuous miners and long wall miners, but typically have not been effective because they have been installed so as to measure where the mining equipment has been rather than where the cutter is going. One reason that gamma detectors have often been used in a non-effective manner is that the detectors could not physically survive if subjected to the environment in locations where they would be most effective.
Numerous other approaches have already been conceived and tested over the years for directing or guiding mining equipment. Most of these concepts have not proven to be commercially successful due to technical deficiencies, implementation problems, and cost. Many types of sensors have been incorporated into control systems to monitor the shape, profile and characteristics of the formations through which the mining equipment is cutting and to make cutting decisions on where to point subsequent cuts based on this information. Thus, these approaches fail not only due to practical implementation problems but also because of a fundamental flaw with the concept. Knowledge about the shapes, profiles, or characteristics of the formation being passed through does not provide accurate information about the formation just ahead, for which the cutting decisions must be made.
In most of the examples above, the control systems employed have been complex and expensive. A typical approach is to -use a gravity-referenced or inertial-referenced control system, with various other sensors added. Some of these control concepts have been referred to as “horizon control systems.” A horizon control system typically uses the gravity-referenced sensors or inertial-referenced sensors that keep track of the orientation of the continuous miner and the profile of the roof and floor.
In principle, the horizon control system approach is to control the mining equipment by use of guidance systems adapted to mining applications. However, as discussed above, guidance systems cannot generate accurate information about the formation to be cut because the historical information that they log in detail is not a valid indicator of what is ahead. Moreover, these guidance systems are complex and costly.
It is described in co-pending U.S. application Ser. No. 09/811,781 that in underground coal mining, a properly designed and properly positioned, forward-looking armored gamma detector, in combination with a suitable control system, can be effective for reducing the amount of rock taken while extracting an increased amount of coal or other mineral. A mining control system that incorporates such forward-looking detectors is referred to as a “rock avoidance system.” The use of rock avoidance systems can help cut the floor of the mine very smoothly and simplify the job of the operator. Rock avoidance systems allow continuous miner operators to be positioned further from the coal face, thus reducing health hazards.
However, even when used with forward-looking rock detectors as described in co-pending U.S. application Ser. No. 09/811,781, these horizon control systems do not utilize the data generated by the rock detectors as fully as it could be used, because the systems are conceived and designed to guide or point, determining the direction to move, rather than being appropriately responsive to sources of external intelligence such as armored gamma detectors. In addition, inertial or gravity referenced systems are not typically designed to provide precision and timely measurements of cutter movements that will allow a rock detector to achieve maximum sensing accuracy.
Rock avoidance systems that rely upon complex guidance systems are costly and, complicated and have some inherent inefficiency resulting from their methodology. A need now exists to provide an accurate rock avoidance system that is simple, economical and easy to install and operate. There is also a need for such a rock avoidance system for use on long-wall mining equipment as well as continuous mining equipment.